Ice Ages

Abstract

Ice ages are periods of the Earth's history characterized by glacier advance and cold climate. The response of the Earth's
systems to ice ages includes extinctions and migrations of the biosphere, expansion and contraction of oceans and lakes, and
the waxing and waning of glaciers.

Ice age variations on three time scales. (a) Oxygen isotope stages as proposed by Cesare Emiliani (1950). Interglacials are
odd‐numbered stages (blue), and have lower 18O/16O ratios. Glacials are even‐numbered (red) and have higher 18O/16O ratios. Stages 3 and 4 are intermediate, but follow Emiliani's original publication, as does the orientation of the y‐axis. The saw‐toothed pattern of the glacial–interglacial cycles is emphasized by the blue line. (b) Oxygen isotope variations
of the past 5 000 000 years as recorded in DSDP 846, data provided by Ralf Tiedman. Note the long‐term increase of the 18O/16O ratios, the beginning of the Pleistocene ice age, and 100 000 year periodicity of the last 500 000 years. (c) Older ice ages
plotted on a graph of atmospheric carbon dioxide concentration relative to a modern value of ‘1’. Data after Berner (1994).